The growth of wireless communications has freed users from the shackles of traditional landline telephone devices. Although wireless networks helped create “mobile terminals” (or more generally “mobile devices”),e.g. wireless phones, even this level of mobility does not meet some users' personal mobility. Users are not truly free to roam wherever they desire and still be able to place a call. Users can only use a mobile device/terminal (hereafter both “device” and “terminal” will be used synonymously) within a specified geographic region serviced by the user's network provider. If the user ventures outside the coverage area of her network, or if the user roams into another area serviced by a different network, the user is unable to complete a call.
“Seamless global roaming” is a desirable feature to users of wireless terminals. Simply stated, seamless global roaming allows users to roam across networks using different technology protocols. Seamless global roaming, however, presents several new challenges for communications networks. The main challenge is protocol conversion by a so-called “home location register” (HLR) as a mobile terminal moves between networks having different “mobility management” protocols. One solution for seamless global roaming includes standardizing the signal translations between today's predominate telecommunications protocols: the American National Standards Institute-41 (ANSI-41) and the Global System for Mobile Communications (GSM). The proposed solution is based on a one-to-one mapping between the two protocols. This solution, however, is unable to accommodate the introduction of new protocols, such as “session initiation protocol” (SIP). SIP, which allows for call deliveries between the Internet and other networks, has been gaining favor in the telecommunications industry. SIP is being used with increasing frequency because it is capable of supporting mobility over the Internet as well as over public switched telephone networks (PSTNs).
Today, a user operating a mobile terminal within a network she is visiting may receive service (e.g., wireless telephone service) even though the service is being provided by different service providers from the ones the user is registered with, provided the correct protocol is used to handle her calls. In a GSM network, roaming is facilitated by inserting a subscriber identity module (SIM) card into the terminal. The SIM helps the network identify a “subscriber” and locate the appropriate service profile. The SIM card works well for subscribers roaming in wireless GSM networks. However, the SIM card approach does not support roaming between wireless and wireline networks, or between networks operating under different protocols.
Another approach to facilitate global roaming is the use of intelligent networks (IN). Intelligent networks were introduced to enhance personal communications services, such as voice messaging, data, image, and video communications and to allow interworking between wireless and wireline networks. Global roaming was supposed to be supported in INs by assigning each subscriber a “universal personal telecommunications” (UPT) number. A service provider maps assigned UPT numbers to mobile or PSTN phone numbers. However, in the case of mobile terminals, once the provider's service control point (SCP) obtains a mapped number, an additional translation is required. A HLR must be interrogated to obtain a routing number for the mobile phone number of the subscriber in order to complete a call. This additional interrogation requirement increases the cost and complexity of the service.
Another concern is integrating the SIP protocol into existing telecommunications networks while maintaining global roaming. SIP allows for the delivery of calls between the Internet and wireless networks through SIP/PSTN gateways. The GSM/ANSI-136 Interoperability Team (GAIT) defined a new functionality called “interworking and interoperable functionality” (IIF) that is used to support global roaming. An intermediary agent, known as an IIF translator, translates messages between the GSM and ANSI-136 protocols. The IIF translator uses two databases, one for each subscriber profile for each protocol, to translate between the two protocols. The complexity of scaling such a one-to-one system by adding n protocols increases by at least n2. For example, adding SIP to such a systems would require adding two additional IIF translators. Adding n additional protocols to such a system would require at least n2 additional IIF translators. This makes deployment difficult and expensive, since several different IIF translators would have to be modified.
Thus, there is a need in the art for techniques that allow communications between wired and wireless networks which are operating using different protocols. In particular, there is a need in the art for simple and inexpensive techniques that support multiple, protocol interfaces to allow global roaming across a number of diverse networks.